As dark falls and activity in the woods slows, these forest-devastating beasts slither out of their secure houses and begin their night’s work. Gnawing, chopping, digging and collecting materials all night long, their business is construction – and with it destruction.
Beavers were introduced to Tierra del Fuego in 1946. At this time, under the presidency of Juan Domingo Perón, Tierra del Fuego was classed as national territory rather than a province in its own right and was under control of the Argentine navy. As an initiative to boost the fuegiuno economy, Perón’s navy decided to import 25 beaver couples from Canada to the southern Argentine island with the idea of breeding the animals for their fur.
Canadian beavers alternate seasonally between two types of fur coat. In the cold frosty winter they grow a thick fluffy coat, ideal for the fur industry. When the warmer damper weather approaches they shed this soft fluffy fur and replace it with a lighter but coarser waterproof coat. In Tierra del Fuego, as the beavers have adapted to the more temperate and wet climate, they have no need for their warm winter coat and stick with the summer one all year round.
With no fluffy winter coats, the beavers are not hunted for their skins but left to multiply in this land with no natural predators.
Now there are an estimated 150,000 beavers living on the island – twice the human population – and they have spread on to the South American continent.
These systematic engineers work throughout the night changing the courses of rivers, chopping down trees and building dams. Their process of destruction begins as they burrow underwater to break through a river bank and open a new channel. Meanwhile they saw down trees with their sharp teeth and use the trunks to build a dam further down the valley. The river water, flowing along this new course, is stopped by the dam, creating a pool.
The beavers inhabit dry hollows inside the dams but above water level. The entrance to these dens is via the water which protects the beavers from land predators. The still pools and wetlands created by their dams are ideal environments for the aquatic plants that these strict vegetarians feed on.
Dr. Adrián Schiavini, from the Austral Centre of Scientific Investigations (CADIC), explains the negative impacts that beavers are having on the ecosystem in Tierra del Fuego: “The pools of water generated behind the dams flood hundred-year-old trees and natural vegetation. The dams also reduce water flow which hinders the cycling of nutrients.”
Everything that was living on the land where this new pool of water has been created is drowned. But the beavers cleverly let some water flow through the dam so that a new pool can be created further downstream for their offspring to inhabit.
Schiavini describes the scale of the impact: “Eventually, from one broken river bank they create a series of pools guarded by dams which flood a huge area of woodland, not to mention the deforestation they have caused to generate building materials.”
The devastating effect is amplified as one beaver may build several dams in his lifetime. “When the pools get filled with sediment, the beavers will abandon their home and find a fresh spot to build new dam,” explains Schiavini.
These territorial mammals have no natural predators in Tierra del Fuego and, as young beavers leave home at two years old to build their own dams, the rate of their destruction is phenomenal.
“In Canada the number of beavers is controlled by their predators: wolves, links and bears,” Schiavini tells me. “Some experts think that pumas could be a predator on the continent, but it is only speculation,” he adds.
Researchers have been investing the options for solving the problems caused by the beaver. The team of biologists at CADIC have come to the conclusion that there are two possibilities: “Either we decide to control the number of beavers, which implies a continued effort and surveillance of the situation, or we opt for a complete eradication of the species which requires a one-off large investment of time, money and effort but could solve the problem permanently.”
The question remains, is it worth the huge effort and cost?
“The purpose of eradicating the beavers would be to restore the natural forest and vegetation,” explains Schiavini. “If this cannot be achieved there is no point in removing the beavers.” CADIC is currently carrying out research to determine whether the forest can be restored naturally or would need human intervention.
As the beavers are presently in both Argentina and Chile, the respective governments have agreed to collaborate in their efforts to find a solution.
Until recently the government was relying on local initiatives and small incentives. They offer locals $15 for every hunted beaver. Given that beavers are extremely difficult to hunt, being nocturnal and having an ability to hide underwater, the $15 incentive has not been enough to encourage many fueguinos to take up beaver hunting as a serious vocation.
However, in September this year the two governments signed an agreement to work towards the eradication of this destructive species. This will be a long process and the operational phase is not expected to begin for at least five years.
CADIC is working closely with the government to ensure that the eradication will be managed in an appropriate way. Schiavini says, “There are still many research questions to be answered before we can start thinking of the actual eradication of the beavers. We need to find a way of being sure that the beavers have been fully cleared out, for example.”
Beavers have become an iconic symbol of Tierra del Fuego and beaver spotting is advertised as a tourist attraction. CADIC is encouraging the tourist industry to avoid this image of a cute cuddly beaver and tour guides to explain why beavers are a nuisance on the island.
These beavers certainly provide testament for the old saying ‘busy as a beaver’, and until they are slowed down, their destructive activity will continue to play havoc with the ecosystem in Tierra del Fuego.